Terminal device



Nov. 3,1970 SHERLOCK 3,538,240

TERMINAL DEVICE Filed Aug. l2, 1968 BYl Z6 ,l Z3

United States Patent Oihce Patented Nov. 3, 1970 ABSTRACT OF THEDISCLOSURE A terminal device comprising a strip of heat shrinkableplastic material having a plurality of passageways therethrough in eachof which is located a socket contact for receiving a pair of conductorterminating pins. Once all of the pins have been properly located, thestrip is shrunk down around them to firmly secure them in place and toestablish good electrical contact between the pins and the socketcontact.

BACKGROUND OF THE INVENTION Various mechanical terminal devices havebeen provided for establishing proper electrical connections betweengroups of electrical wires. Most of these devices rely on some type ofspring biased socket contact to grasp the end of a suitable terminatingpin which is crimped or otherwise fastened to the end of the conductor.The pressure of the spring portion of the socket contact on the pinestablishes a wiping action between the two surfaces and provides theelectrical contact. The socket contacts are either single ended withsuitable connections formed on the device between pairs of them or aredouble ended and provide their own electrical contact. While suchterminal devices are satisfactory for many applications, they are not asreliable as desired because the force exerted on the pin by the springtines of the socket contact is often not great enough to withstand theforces, such as vibration, tending to pull the conductor out of thecontact. Moreover, the devices of this type olfer no environmentalprotection to the contact and thus special provision must be made forsuch protection.

SUMMARY OF TlHE INVENTION According to the present invention, a terminaldevice is provided in which a plurality of double ended socket contactsare embedded in passageways formed in a strip of heat recoverablematerial. The spring forces of the contact are suicient to hold the pinswhich are attached to the various conductors in place until the wiringassembly is completed and checked. The strip of material can then beheat recovered so as to cause the spring tines of the socket contacts toengage the pins even more rmly to produce a superior electrical contact,and also to engage the portion of the pins exterior of the socketcontact to securely grasp them and prevent their retraction from theterminal strip. The plastic material of which the strip is made providesgood environmental protection as it completely encapsulates theelectrical connection. The device of the present invention has thefurther advantage of having the ability to be heated and shaped intounique configurations and cooled to allow mounting in irregular areas.While the conductors are prevented from being Withdrawn under normaloperating conditions, if it becomes desirable to withdraw them, theterminal strip can again be heated so that the material presses againstthe pins with only elastic force, thus permitting removal of the pinswith only slightly greater diiiiculty than was involved beforeshrinkage.

It is therefore an object of the present invention to provide a terminaldevice for electrical conductors utilizing a strip of heat shrinkablematerial.

These and other advantages of the present invention will become moreapparent upon reference to the accompanying description and drawings inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of astrip of heat recoverable material as used in the present inventiontogether with a typical socket contact;

FIG. 2 is a cross-sectional view taken along lines 2 2 of FIG. 1;

FIG. 3 is a cross-sectional view similar to FIG. 2 but after thematerial has been partly recovered around mandrels;

FIG. 4 is a cross-sectional View similar to FIG. 2 but showing theterminal device ready to receive a pair of pins;

FIG. 5 is a cross-sectional view of the terminal device of the presentinvention after the pins have been installed and the material heatrecovered;

FIG. 6 is a cross-sectional view of a modification of the terminaldevice showing pins partially inserted therein; and

FIG. 7 is a cross-sectional view of the device of FIG. 6 after the pinshave been installed and the material heat recovered.

DESCRIPTION OF THE INVENTION Turning now to the drawings, a block orstrip 10 of heat recoverable material is molded or otherwise providedwith a plurality of passageways 11 which extend completely through thestrip. Any polymeric material capable of being crosslinked such as byirradiation or chemical treatment may be utilized in the presentinvention. Preferably, the polymeric material is a heat recoverablematerial capable of having the property of elastic memory imparted toit. Typical heat recoverable materials include crosslinked polymers, forexample, crosslinked polyoleins; crosslinked polyvinylchloride;crosslinked polyvinylidene halides; for example, crosslinkedpolyvinylidene fluoride; crosslinked ethylenevinylacetate copolymers;crosslinked ethylenelthylacrylate copolymers; crosslinked polyamides;etc. The strip 10 could also be fabricated of noncrystalline polymericmaterials capable of having the property of plastic or elastic memoryimparted thereto such as polyurethane and ionmers and elastomers such assilicone. Materials having the property of plastic memory or elasticmemory are equally useful in the present invention; therefore theseterms are used interchangeably herein and are meant to be mutuallyinclusive.

The strip 10 is molded with the holes 11 and then each hole is expandedby heating the material above its crystalline melting pont and insertinga steel rod having a diameter larger than the diameter of the originalhole. Once the parts cool the rods are removed. The material around theholes is thus dimensionally changed from an original heat stable form toan independently heat unstable form capable of moving in the directionof its original -forrn upon the application of heat alone.

Positioned within each of the holes 11 in the strip 10 is a double endedsocket contact 12 which may be of the conventional type, i.e., a tube ofcopper or the like slotted at each end to form spring tines which arecollapsed on each other to form an elliptical entry. They may also takethe form of a tubular member which is slotted at each end but in whichthe tines are not collapsed on each other prior to heat recovery of thestrip 10, or in which the tines are expanded to form a tapered entrance.In order that the strip will retain the socket contacts 12 and form astop shoulder for the pin contacts, a pair of mandrels 13 and 14 areinserted into the ends of each of the holes 11 as shown in FIG. 3. Theends of the mandrels -13 and 14 have a diameter sufficiently large toseparate the tines of the contact 12 so that recovery of the strip 10will not cause them to be forced together to such a degree as to preventthe access of the pin contacts. The strip 10 is then heated to above itsheat recovery temperature so that it shrinks down around the mandrelsand around the contact 12. Once the part has cooled, the mandrels 13 and14 are removed leaving the double ended socket 12 captured in the centerof the passageway 11. Because a small amount of recovery occurs afterthe mandrels are removed, the holes recover an additional small amount.The initial spreading of the tines by the mandrels must be enough toallow for this additional shrinkage. The resulting structure is shown inFIG. 4. As can be seen, the center portion of the contact 12 is rmlyengaged by the material of the strip 10 while the tines are spaced fromthe wall so that they can receive the pin contacts.

The terminal device is now ready to receive pins 16 and 17 whichterminate the ends of conductors 18 and 19, respectively. As shown,these pins are provided with a tapered forward end 20 for ease ofinsertion and a circular section 21 behind the taper. They are alsoprovided with a collar 22 which serves as a locating shoulder. The pins16 and 17 are inserted into the passageway 11 until the collar 22 abutsthe ends of the tines 15. The pins are held in position by the tineswhich provide a wiping action on the section 21 of the pin.\

After all of the conductors have been positioned and the circuit testedor checked to determine that it has been correctly wired, the strip 10is again heated to above its heat recovery temperature. This causes thematerial surrounding the holes 11 in the strip 10 to recover completelydown around the contacts and force the spring tines tight around thepins. The recovery force of the shrinking of the crosslinked materialhelps to provide a good electrical contact. The pins cannot be removedbecause the material of the strip 10 recovers down around the collar ofthe pin and moves into slots 23 formed in the pin for that purpose. Thefinal structure is shown in FIG. 5. As will be obvious to those skilledin the art, proper selection of the material from which the strip 10 isfabricated will result in a moisture seal being formed around the pinsor, if desired, only a moisture barrier or no seal at all.

Once the material of the strip 10 has been heat recovered down aroundthe pins 16 and 17, it is very ditiicult for them to be withdrawn andthus the terminal device is extremely resistant to degradation of theelectrical contacts by vibration or other external forces. Moreover, theterminal device inherently provides its own environmental protection. Ifit is desired to again remove the pins, this can be accomplished byheating the strip to above the heat recovery temperature of the materialfrom which it is fabricated. If this is done, only the elastic force ofthe material will press against the pins and they can be removed withonly slightly greater diculty than was involved before shrinkage of thestrip 10. It will be obvious to those skilled in the art that the strip10 can be molded in any desired shape so that the ter- 4 minal device isextremely versatile. It will also be obvious to those skilled in the artthat the shape of the pins and the nature of the socket contact can bevaried to suit any particular purpose without departing from the scopeof the present invention.

Such a modified pin and socket contact construction is shown in FIGS.'6i and 7. In these figures, the socket contact 25 has tines 26 whichextend outwardly to form a tapered pin receiving opening. The tines 26are provided with a ridge 27 which cooperates with a groove 28 formed inthe pin 29. The pin 29 is provided with a collar 30 which engages theends of the tines to locate the pin. The conguration of the assemblyafter recovery is shown in FIG. 7.

As a specific example of the manner in which such a terminal strip can`be constructed, a slab of 0.188 inch thick chemically crosslinkedpolyolefin was cut into a strip one inch wide. Holes 0.375 inch apartwere then drilled across the width of the strip with a 0.062 inch drill.The material was then heated above the crystalline melting point and theholes expanded by inserting a 0.150 inch steel rod into each hole. Oncethe parts had cooled, the rods were removed and a two-piece, steppedmandrel having an outside diameter of 0.100 inch was inserted into eachhole, the mandrels carrying the socket contacts. The part Iwas againheated causing it to recover down on the mandrels. Once the part cooled,the mandrels were removed leaving the double ended sockets positionedwithin the strip. The socket members each were made of 0.010 inchberyllium copper former into a tube .500 inch long having a 0.100 inchinside diameter. The tube was slotted 0.188 inch deep by 0.015 inch widefrom each end on the opposite side from the formed edge. A section wasalso taken out of the center of the tube to insure maximum spring ofeach tine. The pins were then inserted and the material again heated toabove its recovery temperature to cause it to recover around the pinsand socket contact in the manner previously described.

What is claimed is:

1. A device for receiving and holding a plurality of ob- Jectscomprising: a block of heat recoverable material having a plurality ofholes formed therein, the material around at least two of said holeshaving been dimensionally changed from an original heat stable form toan independently heat unstable form capable of moving in the directionof its original form upon the application of heat alone; and clampingmeans positioned within each of said dimensionally changed holes andadapted to mechanically engage in each of said dimensionally changedholes at least one of said objects, said material of said block beingpartially recovered to hold said clamping means in place, the devicebeing further heat recoverable to encapsulate said clamping means andterminal portions of said objects, and admitting of the subsequentremoval of the encapsulated terminal portions upon the application ofheat.

2. The device of claim 1 wherein said holes extends through said blockand wherein each of said clamping means has two ends, each of said endsbeing adapted to mechanically engage one of said objects.

3. The device of claim 1 wherein said clamping means comprise a tubularmetallic members having exible portions bent inwardly by said partialrecovery of said material.

4. The device of claim 2 wherein said clamping means comprise a doubleended socket contacts.

5. A device for receiving and holding a plurality of pins terminatingcorresponding electrical conductors, comprising: a block of heatrecoverable material having a plurality of holes formed therethrough,the material around at least two of said holes having been dimensionallychanged from an original heat stable form to an indepcndently heatunstable form capable of moving in the direction of its original formupon the application of heat alone; and a plurality of double endedsocket contacts each adapted to mechanically engage a pair of said pins,each of said contacts being positioned within one of said dimensionallychanged holes, said material of said block being partially recoveredaround said contacts to hold them in place, the device being furtherheat recoverable to encapsulate said contacts and said pins andadmitting of the subsequent removal of the encapsulated pins upon theapplication of heat.

6. A terminal assembly comprising: a block of heat recoverable materialhaving a plurality of holes formed therethrough; a plurality of doubleended socket contacts, one of said socket contacts positioned in each ofat least two of said holes; and a plurality of electrical conductorsterminating in pins, each of said pins being inserted into one of saidsocket contacts positioned in said holes, said material of said blockbeing heat recovered into engage- References Cited UNITED STATES PATENTS1,975,885 10/1934 Wellman 339-205 2,396,725 3/1946 Thomas l74-88 XR3,320,355 5/1967 Booker 174-84 DARRELL L. CLAY, Primary Examiner U.S.Cl. X.R. 339-205

